The latest prototype cell phone based on a direct methanol fuel cell (DMFC) made its debut on Tuesday at the Ceatec show in Japan.

The modified Toshiba T002 handset is being shown by Japanese carrier KDDI as a research and development device and shows some improvements in technology based on previous prototypes, but there's still no word on when a phone based on the technology will be available.

DMFCs produce electricity from a reaction between methanol, water and air. The only by-products are a small amount of water vapor and carbon dioxide, so DMFCs are often seen as a greener source of energy than traditional batteries.

In the prototype cell phone, the fuel-cell unit also includes a lithium ion battery. The battery is needed to cope with the spikes in power demand from the cell phone between times when it sits idle and when it's used to make a call or browse the Web. The fuel cell is best-suited to supplying a constant amount of power so the battery acts as a buffer to ensure the cell phone works smoothly.

That combination gives the phone an overall life, on a single charge of methanol, of about 320 hours. That's about three days longer than the commercial T002 phone can manage.

But the biggest advantage of DFMC isn't the longer battery life but that it can be refilled in seconds with a squirt of methanol rather than having to wait an hour or two for the battery to be recharged.

For now, the addition of a fuel cell means the phone's thickness is about twice that of the equivalent commercial version of the phone. But at 22 millimeters this latest version is about half the thickness of a prototype shown several years ago and KDDI said it continues to work towards a thinner handset.

The phone is based on a fuel cell developed by Toshiba.

Toshiba has been promising a commercial battery charger based on the same fuel-cell technology for several months but has yet to announce a commercial product. Two months ago, the company's new president said it would be launched by the end of September but that deadline passed a few days ago without anymore information on the device.

The charger will be a portable device that can be used to charge the batteries in portable gadgets such as cell phones, music players and portable game devices instead of plugging them into an electrical outlet.

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